Chainings - help with interchangeability! (Triple)

[stoatsngroats]

I have a Pioneer triple (it's on my tandem,and no, I've never heard of them either!),and having just changed chain and cassette.
The middle ring is unuseable, as even a slight bit of effort on the pedals makes the chain slip. The bigger, and smaller rings are much better, although I haven't riden standing on the pedals (I have a back problem, causing pain, so just fettling today!)
The teeth on the middle are very pointy, like sharks fins, on the big ring the teeth are slightly finned, and on the small ring, the teeth are square topped.
I think the cranks are square taper, and they are fitted to the rings with 4 bolts.

So, my question, can I change just the 2 worn rings, if so, is i just a matter of removing the crank, and unbolting the 2, or can I just unbole the chain rings, leaving the crank on?
Or do I have to replace all three rings, and the cranks?
Thanks for your guidance!

SnG

 

[slowmotion]

I don't know about your particular bike but with my triple I can remove the big and middle ring without taking off the cranks. Getting the middle one off can be a bit of a head-scatcher but I got there in the end. BTW, Spa Cycles is a good source of chain rings.

 

[stoatsngroats]

Thanks slowmotion, I'll take a look!

 

[Levo-Lon]

Take the pedal off and they should come off without removing cranks..
check bolt circle..ie 104bcd...

 

[mrandmrspoves]

It is possible to change rings with the crank still on the bike/tandem - but it is so easy to take the crank off that you will save time and effort by doing so (assuming you are right about your BB being square taper)
A crank extractor tool is only going to set you back £5 - £10.
Measure the distance from the middle of one chain ring bolt to the middle of the next chain ring bolt as that is the measurement you will need to ensure you get correct replacements. You can replace rings individually but the rings are often quite expensive as single items - so sometimes it makes sense to just buy a new triple especially if 2 or 3 rings are getting close to needing replacement anyway.

 

[stoatsngroats]

Ok, I got the crank off, and here are the 2 outermost C/rs. are they worn!?

32t and 44t. front side of 32t shown ^^^^^
I think they are!

The rear of the 32t has some strange things on - does anyone know what the things shown in the red circle are, or are for..?

Lastly, is there a particular model typr I have to use - I'm using a (new) narrow chain, and new cassette, I was thinking of this...
http://www.sjscycles.co.uk/shimano-...d-4-arm-middle-chainring-black-32t-prod28749/

(Edited to correct link!)
Any advice?

Thanks

 

[mrandmrspoves]

The strange things that you refer to are called ramps. Modern chain rings have ramps and non symmetrical teeth to help gear changes. The ramp is designed to help lift the chain onto the ring.

 

[mrandmrspoves]

The teeth in your photo look quite worn - but not the worst I have seen by a long chalk. As you have replaced the chain and cassette, it would make sense to change the rings too as otherwise they will increase the wear on the new chain and cassette and could start slipping when you put the power down.

The chain rings that you buy need to be rated as correct for the number of gears on your rear derailleur - that tends to be 6,7 & 8 or 9&10.

 

[stoatsngroats]

The chain rings that you buy need to be rated as correct for the number of gears on your rear derailleur - that tends to be 6,7 & 8 or 9&10.

Thanks Mrsandmrspoves, for this info. I have 8 speed Acera flatbar sti shifters, cassette 11-34, and an HG narrow chain. I had this extreme chain slip on the middle ring, much less so on the inner and outer ring - the chain just slipped even with the slightest pressure! (Hence this investigation!)
The thing i'm unsure about is what the differences are between these 3 Shimano C/Rs, and could I use any of the on my current set up -

• shimano-fc-m532
• shimano-fc-m590
• shimano-fc-m660

i.e. are these interchangeable?

Any further help you can offer is appreciated!

thanks
SnG

 

[mrandmrspoves]

The middle ring tends to be the one people tend to use most - so usually the one that wears out first. If your chain is slipping at all on the largest and smallest rings, I would get them swapped out now as well as doing the middle ring, and if you're doing all 3 it will be almost as cheap (maybe cheaper if you went to some of the lower spec models) to just buy a new triple.
Chain rings can normally be mixed and matched, as long as you get an inner, middle and outer ring with the correct bolt diameter.

As far as I can tell, the chain rings you are looking at would do fine - but others may be able to give you better advice re this.

 

[stoatsngroats]

That's great mrandmrspoves - thanks again! I went for the M410 32t and 42t chainrings in the end, for £22 posted! (from Wiggle)
It'll be interesting to see how I get on!

 

[stoatsngroats]

New ones arrived today, I'm hoping they'll make a difference!
32t old and new...

and 42t old and new...

I'll post once they're on, and we're back riding!

thanks all for your thoughts, and guidance

Fitted, tested OH NO!!! chain slip on middle ring, so a quick test ride with the stoker around the block confirmed the WORST mistake.... so, back home, turn the middle ring around to the correct way, and a 2nd test ride, and it works perfectly! Woop woop!!

Thanks again guys!